JPH09280923A - Liquid level detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably detect a liquid level in a transparent pipe without being affected by the dimension of the outer diameter of the transparent pipe. SOLUTION: Light is projected onto the inner circumference of a transparent pipe A from a projection lens 19b to detect the level of a liquid within the transparent pipe A based on the quantity of the reflected light. In the case of this structure, support parts 18a and 18b are formed on a holder where the projection lens 19b is housed and the support parts 18a and 18b contact the outer circumferential surface of the transparent pipe A to mount the holder on the transparent pipe A. The projection lens 19b is so arranged that light is projected to a specified part along a parallel line with respect to an axis line of the transparent pipe A in an inner circumference part of the support part 18b. A light shielding plate part contacts the outer circumferential surface of the transparent pipe A at a specified part along a parallel line with respect to the axis line of the transparent pipe A out of a contact part between the support part 18b and the transparent pipe A.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid level detecting device for detecting the liquid level in a transparent pipe.

[0002]

2. Description of the Related Art For example, when detecting the liquid level in a tank, a transparent pipe connected to the tank is equipped with a liquid level detecting device so that the liquid level in the transparent pipe (the liquid level at the same level as in the tank). Is being detected. As shown in FIG. 11, this liquid level detecting device has a configuration in which light is projected from the light projecting means 1 to the transparent pipe A and the reflected light from the transparent pipe A is received by the light receiving means 2.

In this structure, an arc-shaped recess 3 is formed in the holder having the light projecting means 1 and the light receiving means 2, and in detecting the liquid level, the supporting portions (both ends) 3a of the recess 3 and 3b is brought into contact with the transparent pipe A, and light is projected from the light projecting means 1 with the holder stably attached to the transparent pipe A.

Here, when there is a liquid surface at a predetermined height in the transparent pipe A, the projection light from the light projecting means 1 travels straight through the liquid through the inner peripheral surface of the transparent pipe A. Therefore, since the amount of light received by the light receiving means 2 is below the reference value, it is determined that liquid is present. Further, when there is no liquid level at a predetermined height in the transparent pipe A, the projection light from the light projecting means 1 is reflected by the inner peripheral surface of the transparent pipe A toward the light receiving means 2 side. Therefore, the light receiving means 2
Since the amount of received light of is higher than the reference value, it is determined that there is no liquid.

[0005]

In the conventional liquid level detecting device, as shown in FIG. 11, supporting portions 3a and 3b are provided.
Was projecting light toward the middle part of. Therefore, FIG.
As shown in FIG. 5, when the outer diameter of the transparent pipe A changes, the light projection point on the transparent pipe A changes, and there is a risk that the inner peripheral surface of the transparent pipe A will not be exposed to light. Therefore,
The detection area was enlarged with the increase in the light beam of the projected light and the light receiving area of the light receiving means 2, and the difference in the outer diameter dimension of the transparent pipe A was dealt with.

However, in the liquid level detecting device,
Bubbles rising in the transparent pipe A enter the detection area,
The projection light may be reflected by the bubbles. On the other hand, when the detection area of the device is expanded, the light receiving means 2 receives the reflected light from the air bubbles, and although the liquid level is at a predetermined height in the transparent pipe A, it is erroneously determined that there is no liquid. The possibility arises. In particular, as shown in FIG. 13 (a), the transparent pipe A
When the outer diameter of the transparent pipe A is small, the ratio of the detection area to the hollow portion of the transparent pipe A increases, so that the risk of malfunction of the device also increases.

In order to prevent this malfunction, it is effective to reduce the light beam and light receiving area of the projected light and narrow the detection area. However, if the detection area is narrowed, the applicable outer diameter of the transparent pipe A is restricted.
As described above, providing a wide outer diameter dimension of the transparent pipe A that can be dealt with and preventing erroneous operation are contradictory. Conventionally, there is a liquid level detection device that can solve both at once. The reality was not to do it.

Further, in the conventional liquid level detecting device, as shown in FIG. 11, the holder is provided with the light shielding means 4 so that the projection light reflected by the outer peripheral surface of the transparent pipe A is shielded.
The projection light reflected by the outer peripheral surface of the transparent pipe A is prevented from entering the light receiving means 2 and causing the device to malfunction.

However, conventionally, the light-shielding means 4 is arranged in the intermediate portion between the supporting portions 3a and 3b. Therefore, when the device is attached to the transparent pipe A having a small diameter, the light-shielding means 4 is arranged so that the tip end portion thereof contacts the outer peripheral surface of the transparent pipe A.
It was necessary to set the length dimension of. Therefore, when the device is mounted on the transparent pipe A having a large diameter, a gap is created between the transparent pipe A and the tip portion of the light shielding means 4, so that the projection light reflected by the outer peripheral surface of the transparent pipe A is received through the gap. There was a risk that light would enter the means 2. Then, the ratio of the difference in the amount of light received depending on the presence or absence of the liquid to the amount of light received by the light receiving unit 2 becomes small, so that the S / N ratio decreases,
As a result, it becomes difficult to detect the stable liquid level.

In order to prevent the projection light reflected by the outer peripheral surface of the transparent pipe A from entering the light receiving means 2, there are the following methods (1) and (2). (1) As the light shielding means 4 is moved according to the outer diameter of the transparent pipe A, the tip of the light shielding means 4 is constantly brought into contact with the transparent pipe A. (2) For the transparent pipe A having the largest outer diameter, the light projecting means 1 is designed so that the reflected light to the light receiving means 2 side is reduced as much as possible.
To the transparent pipe A. Then, since the light projecting point is displaced inwardly of the transparent pipe A with respect to the transparent pipe A having a small diameter, the reflected light to the light receiving means 2 side is further reduced.

However, in the case of the configuration (1), since it is necessary to provide the holder with the moving mechanism of the light shielding means 4, the configuration is complicated, and as a result, the cost is increased. At the same time, since it is necessary for the operator to move the light shielding means 4 each time the outer diameter of the transparent pipe A changes, it is difficult to say that it is practical in general. In addition, in the case of the configuration of (2), since the ratio of the detection area occupying the hollow portion of the transparent pipe A having a small diameter is increased, the risk of malfunction of the device due to air bubbles is further increased.

The present invention has been made in view of the above circumstances, and a first object thereof is to solve all of the problems in that the corresponding outer diameter of the transparent pipe has a width and the malfunction is prevented. A liquid level detecting device is provided. The second purpose is to stably detect the liquid level by blocking the reflected light on the outer peripheral surface of the transparent pipe without inviting malfunction due to air bubbles and complicating the configuration accompanying the provision of the moving mechanism. A liquid level detecting device is provided.

[0013]

A liquid level detecting device according to a first aspect of the present invention is made to achieve the first object, and is provided with a holder and a circular cross section. A pair of supporting portions that come into contact with the outer peripheral surface of the transparent pipe, a light projecting unit that is provided in the holder and projects light onto the inner peripheral portion of the transparent pipe, and a light emitting unit that is provided in the holder and is projected from the light projecting unit. Light receiving means for receiving the light reflected by the inner peripheral surface of the transparent pipe, the light projecting means,
It is characterized in that light is projected onto a predetermined portion of the inner peripheral portion of the transparent pipe, which passes through the vicinity of the one support portion and is along a line parallel to the axis of the transparent pipe.

According to the above means, the light is projected onto a predetermined portion of the inner peripheral portion of the transparent pipe in the vicinity of one of the supporting portions and along a line parallel to the axis of the transparent pipe. For this reason,
Since the variation of the projection point due to the difference in the outer diameter of the transparent pipe is minimized, it is not necessary to enlarge the detection area. Therefore, it is possible to prevent the device from malfunctioning due to the reflected light from the bubbles with respect to the transparent pipes having various outer diameters.

A liquid level detecting device according to a second aspect of the present invention is made to achieve the second object, and the light projecting means comprises:
Light is projected in the vicinity of one of the inner peripheral portions of the transparent pipe, and one of the supporting portions receives the light reflected from the outer peripheral surface of the transparent pipe among the light projected from the light projecting means. It is characterized in that it is provided between the light projecting means and the light receiving means so as to prevent light from entering the means.

According to the above means, the one support portion contacts the outer peripheral surface of the transparent pipe without being affected by the outer diameter of the transparent pipe, and functions as a light shielding means. For this reason, the projection light reflected on the outer peripheral surface of the transparent pipe does not enter the light receiving means, so that the ratio of the difference in the light receiving quantity due to the presence or absence of the liquid to the light receiving quantity received by the light receiving means becomes small. Therefore, S
The / N ratio increases, and as a result, the liquid level is detected stably.

[0017]

FIG. 1 shows a first embodiment of the present invention.
7 will be described with reference to FIG. The present embodiment is for detecting the liquid level in the transparent pipe A made of acrylic. The base end of the transparent pipe A is connected to the bottom of the tank, and the tip end extends vertically upward, and the liquid level in the transparent pipe A is at the same level as in the tank.

First, in FIG. 4, a holder 11 comprises an upper holder 12 made of synthetic resin and a lower holder 1 made of synthetic resin.
3, and a band head 14 is provided on the upper holder 12 and the lower holder 13. Each of these band heads 14 is movable in the directions of arrow A and counter arrow A shown in FIG. 3, and each band head 14 has a hole 14a (only one hole 14a is shown). . A binding band 15 is inserted in each hole 14a.

As shown in FIG. 5, the upper holder 12 and the lower holder 13 are provided with support heads 16 located at the end portions on the transparent pipe A side, and each of these support heads 16 is shown in FIG. As shown, an arcuate recess 16a
Are formed (only one concave portion 16a is shown).
In addition, as shown in FIG.
7 is rotatably mounted, and when the lever 17 is rotatably operated, both band heads 14 are integrally moved in the direction opposite to the arrow A.

Therefore, when each binding band 15 is tightened on the outer peripheral surface of the transparent pipe A, both ends of each recess 16a are held in line contact with the outer peripheral surface of the transparent pipe A, and the holder 11 is attached to the transparent pipe A. It is installed stably. Also, FIG.
When the lever 17 is rotated from the state shown in (1), the binding bands 15 are loosened as the band heads 14 move in the opposite arrow A direction, and the position of the holder 11 can be changed in the vertical direction along the transparent pipe A. .

The curvature of each recess 16a is set to correspond to the transparent pipe A of the plurality of types having the smallest outer diameter. Therefore, the holder 11 is attached to the transparent pipe A.
, The entire inner surface of each recess 16a is transparent pipe A
Contacts the outer peripheral surface of. In addition, the supporting portions 18a and 18b in FIG. 1 refer to both end portions (contact portions with the transparent pipe A) of each recess 16a.

As shown in FIG. 2, an optical fiber 19a and a light projecting lens 19b corresponding to a light projecting means are housed in the right side portion of the holder 11. Then, when a light projecting element (not shown) emits light, light is projected from the light projecting lens 19b to the inner peripheral surface of the transparent pipe A through the optical fiber 19a, and is shown by a broken line β in FIGS. 1 (a) and 1 (b). Thus, the light is made to strike a predetermined portion along the line parallel to the axis of the transparent pipe A in the inner peripheral portion of the support portion 18b.

The projection lens 19b, as shown in FIG. 1 (a), is different from the transparent pipe A having the smallest outer diameter,
A form in which the hollow part is cut off as thinly as possible (width W
Is projected as small as possible). Reference numeral α in FIGS. 2 and 7 indicates an allowable area of the light projecting point of the light projecting lens 19b.

As shown in FIG. 2, an optical fiber 20a and a light receiving lens 20b corresponding to the light receiving means are housed in the left side portion of the holder 11, and the light reflected by the inner peripheral surface of the transparent pipe A is The light is collected by the light receiving lens 20b, and the light receiving element (not shown) is passed through the optical fiber 20a.
Is received by. A liquid level detection circuit (not shown) is connected to the light receiving element, and the liquid level detection circuit compares the amount of light received by the light receiving element with a reference value, so that a predetermined height in the transparent pipe A is reached. It is determined whether there is a liquid level. still,
The two-dot chain lines α1 and α2 in FIG. 1 define the light receiving area of the light receiving lens 20b.

In the holder 11, as shown in FIG.
A light shielding plate portion 21 corresponding to the supporting portion is provided. The light shielding plate portion 21 is integrally formed with the upper holder 12, and has a base portion 21a having a rectangular plate shape and a head portion 21b having a triangular prism shape. And this light-shielding plate portion 2
The head portion 21b of the first shields the projection light reflected on the outer peripheral surface of the transparent pipe A, and therefore follows the line parallel to the axis of the transparent pipe A in the contact portion between the support portion 18b and the transparent pipe A. The predetermined portion is in contact with the outer peripheral surface of the transparent pipe A (that is, it is located on the line segment connecting the upper support portion 18b and the lower support portion 18b as shown in FIG. 4).

Next, the operation of the above configuration will be described. In detecting the liquid level in the transparent pipe A, as shown in FIG. 3, the binding bands 15 are tightened on the outer peripheral surface of the transparent pipe A, and the support portions 18a and 18 of the support heads 16 are provided.
The holder 11 is attached to the transparent pipe A by bringing b into contact with the outer peripheral surface of the transparent pipe A. When the light projecting element emits light in this state, as shown in FIG.
Light is projected onto the inner peripheral surface of the transparent pipe A through b.

Here, when there is no liquid surface at a predetermined height in the transparent pipe A, due to the difference between the refractive index of the transparent pipe A and the refractive index of air, the projected light is reflected on the inner peripheral surface of the transparent pipe A. The light is reflected and enters the light receiving element from the light receiving lens 20b through the optical fiber 20a. Therefore, since the amount of light received by the light receiving element exceeds the predetermined value, the liquid level detection circuit determines that there is no liquid. When the liquid level is at a predetermined height in the transparent pipe A,
Due to the closeness of the refractive index of the liquid and the refractive index of the transparent pipe A, the projection light travels substantially straight in the liquid through the inner peripheral surface of the transparent pipe A.
Therefore, since the amount of light received by the light receiving element is below a predetermined value, the liquid level detection circuit determines that there is liquid.

According to the above embodiment, the light is projected onto a predetermined portion of the inner peripheral portion of the support portion 18b along a line parallel to the axis of the transparent pipe A. Therefore, as shown in FIG. 7, the variation of the projection point due to the difference in the outer diameter dimension of the transparent pipe A is minimized, so that it is not necessary to enlarge the light beam and the light receiving area of the projected light and to enlarge the detection area. .
Therefore, with respect to the transparent pipe A having various outer diameters, it is possible to prevent the device from malfunctioning due to the reflected light from the bubbles.

In addition, regardless of whether the holder 11 is mounted on the small-diameter transparent pipe A or the large-diameter transparent pipe A, of the contact portion between the support portion 18b and the transparent pipe A, with respect to the axis of the transparent pipe A. At a predetermined portion along the parallel lines, the tip portion of the light shielding plate portion 21 substantially contacts the outer peripheral surface of the transparent pipe A. Therefore, the projection light reflected on the outer peripheral surface of the transparent pipe A does not enter the light receiving lens 20b,
The ratio of the difference in the amount of light received depending on the presence or absence of liquid to the amount of light received by the light receiving element is large. Therefore, the S / N ratio increases, and as a result, the liquid level is stably detected.

Further, in order to prevent the light reflected on the outer peripheral surface of the transparent pipe A from entering the light receiving lens 20b, it is not necessary to move the light shielding plate portion 21 according to the outer diameter of the transparent pipe A. The complexity of the structure is prevented, and as a result, the cost increase is suppressed.

In order to prevent the light reflected by the outer peripheral surface of the transparent pipe A from entering the light receiving lens 20b,
It is not necessary to bring the light projecting lens 19b close to the transparent pipe A. Therefore, as shown in (a) of FIG. 1, it is possible to project light in a form in which the width dimension W is as small as possible with respect to the transparent pipe A having the smallest outer diameter dimension. In addition, the occupancy of the detection area is reduced for the large-diameter transparent pipe A, as in the small-diameter transparent pipe A. Therefore, also from this point, malfunction of the device due to bubbles can be prevented as much as possible.

By the way, the wall thickness of the transparent pipe A is generally thinner as the outer diameter is smaller. On the other hand, conventionally, the light projection direction is set so that the occupation ratio of the detection region is as small as possible with respect to the transparent pipe A having the largest outer diameter. Therefore, when the holder is attached to the transparent pipe A having a small diameter, the transparent pipe A is affected by the thin wall, and the occupation ratio of the detection region tends to be further increased.

In this respect, in this embodiment, as described above, the light can be projected in a form in which the width W is as small as possible with respect to the transparent pipe A having the smallest outer diameter.
The occupation ratio of the detection area can be made as small as possible when the diameter dimension of is minimum. Therefore, as shown in (b), the occupancy rate of the detection area is reduced even for the large-diameter transparent pipe A, similarly to the small-diameter transparent pipe A, so that the malfunction of the device due to air bubbles is generally effective. Is reduced.

Further, in detecting the liquid level in the transparent pipe A, a fiber type photoelectric sensor having a structure in which light is projected by the optical fiber 19a and reflected light is received by the optical fiber 20a is used. It is not necessary to incorporate an optical element, a light receiving element, a liquid level detection circuit, etc. For this reason, the device is downsized, and the device can be installed even in a narrow space.

Next, a second embodiment of the present invention will be described with reference to FIG. The same members as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. Hereinafter, only different members will be described. The upper holder 12 and the lower holder 13 are each provided with two support heads 22.
A recess is formed in each support head 22,
As the supporting portions 18a and 18b corresponding to the ends of the recesses come into contact with the outer peripheral surface of the transparent pipe A, the holder 1
1 is stably attached to the transparent pipe A.

Next, a third embodiment of the present invention will be described with reference to FIG. The same members as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. Hereinafter, only different members will be described. A recess is formed in each support head 16, and the support 1 corresponding to one end of the upper recess 1 is formed.
8a and a supporting portion 18b corresponding to the other end of the lower concave portion
The holder 11 is stably attached to the transparent pipe A as a result of the contact with the outer peripheral surface of the transparent pipe A.

Next, a fourth embodiment of the present invention will be described with reference to FIG. The same members as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. Hereinafter, only different members will be described. A recess is formed in the lower support head 16, and the support portion 18a of the upper recess 16a is formed.
The holder 11 is stably attached to the transparent pipe A as a result of the contacts 18b and 18b and the supporting portion 18b corresponding to one end of the lower recess contacting the outer peripheral surface of the transparent pipe A.

In the first to fourth embodiments, light is transmitted to a predetermined portion of the inner peripheral portion of the transparent pipe A in the vicinity of the supporting portion 18b and along a line parallel to the axis of the transparent pipe A. Although projected, the present invention is not limited to this, and the support portion 1
Light may be projected onto a predetermined portion of the inner peripheral portion of 8a along a line parallel to the axis of the transparent pipe A. Reference numeral α'in FIG. 2 indicates an allowable area of this light projecting point.

Further, in the above-mentioned first to fourth embodiments,
Although the light shielding plate portion 21 is integrally formed with the upper holder 12, the invention is not limited to this. For example, the light shielding plate portion 21 may be integrally formed with the lower holder 13 or the upper holder 12 and the lower holder 13.
Or a separate light-shielding plate portion 21 is formed on the holder 11
It may be housed inside.

Further, in the above-mentioned first to fourth embodiments,
Although the light-shielding plate portion 21 is composed of the rectangular plate-shaped base portion 21a and the triangular prism-shaped head portion 21b, the light-shielding plate portion 21 is not limited to this, and may have a triangular cross-section, for example.

Further, in the above-mentioned first to fourth embodiments,
Although the fiber type photoelectric sensor is used, the present invention is not limited to this. For example, an amplifier separated type in which a light emitting / receiving element is directly arranged behind the light projecting lens 19b and the light receiving lens 20b, or an amp built-in type You may use the photoelectric sensor of this.

Further, in the above-mentioned first to fourth embodiments,
A fixed binding band 15 was used to mount the holder 11 on the transparent pipe A, but the present invention is not limited to this. For example, a variable binding band may be used,
You may use a screw fixing type fixing metal fitting.

Further, in the above-mentioned first to fourth embodiments,
Holder 11 on transparent pipe A that projects vertically from the tank
However, the present invention is not limited to this, and may be attached to, for example, the transparent pipe A that projects obliquely upward.

Further, in the above-mentioned first to fourth embodiments,
In FIG. 1, the arrangement of the light projecting means and the light receiving means may be reversed, or the light projecting means and the light receiving means may be arranged above and below the paper surface, or obliquely above and below the paper surface. May be. The point is that, of the inner peripheral portion of the transparent pipe A, either one of the support portions 18a
And 18b, a light projecting means is arranged so as to project light on a predetermined portion along a line parallel to the axis of the transparent pipe A, and at the inner peripheral portion of the transparent pipe A projected from this light projecting means. The light receiving means may be arranged so as to receive the reflected light.

[0045]

As is clear from the above description, the liquid level detecting device of the present invention has the following effects. According to the means described in claim 1, the variation of the projection point due to the difference in the outer diameter of the transparent pipe is minimized. Therefore, since it is not necessary to enlarge the detection area, it is possible to prevent the device from malfunctioning due to the influence of bubbles on the transparent pipe having various outer diameters.

According to the second aspect of the invention, the reflected light on the outer peripheral surface of the transparent pipe does not enter the light receiving means, and the difference in the amount of light received by the presence or absence of liquid occupies the amount of light received by the light receiving means. Since the ratio becomes large, the liquid level can be detected stably. Further, in order to prevent the reflected light on the outer peripheral surface of the transparent pipe from entering the light receiving means, firstly, it becomes unnecessary to move the light shielding means according to the outer diameter dimension of the transparent pipe. Therefore, the structure is prevented from becoming complicated, and the cost increase is suppressed. Secondly, since it is not necessary to bring the light projecting means close to the transparent pipe, the light projecting direction can be set based on the transparent pipe having the smallest outer diameter. For this reason, the ratio of the detection region to the hollow portion of the transparent pipe is reduced, and from this point also, malfunction of the device due to bubbles can be prevented.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention (a diagram showing the principle of liquid level detection).

FIG. 2 is a cross-sectional view of the holder

FIG. 3 is a perspective view showing a state in which the holder is attached to the transparent pipe.

[Figure 4] Front view of the holder

[Figure 5] Side view of the holder

FIG. 6 is a top view of the holder.

FIG. 7 is a diagram showing a variation state of a projection point.

FIG. 8 is a view showing a second embodiment of the present invention (a front view schematically showing a holder).

FIG. 9 is a view corresponding to FIG. 8, showing a third embodiment of the present invention.

FIG. 10 is a view corresponding to FIG. 9 showing a fourth embodiment of the present invention;

FIG. 11 is a diagram schematically showing a conventional liquid level detection device.

FIG. 12 is a view corresponding to FIG. 7.

FIG. 13 is a diagram corresponding to FIG. 1;

[Explanation of symbols]

A is a transparent pipe, 11 is a holder, 18a and 18b
Is a supporting portion, 19b is a light projecting lens (light projecting means), 20b is a light receiving lens (light receiving means), and 21 is a light shielding plate part (supporting part).

Claims (2)

[Claims] 1. A holder, a pair of support portions provided on the holder and contacting an outer peripheral surface of a transparent pipe having a circular cross section, and a holder provided on the inner peripheral portion of the transparent pipe. And a light receiving unit which is provided in the holder and which receives the light projected from the light projecting unit and reflected by the inner peripheral surface of the transparent pipe, wherein the light projecting unit is the transparent pipe. A liquid level detecting device, which projects light onto a predetermined portion of the inner peripheral portion of the transparent pipe that passes through the vicinity of the one support portion and is parallel to the axis of the transparent pipe. 2. The light projecting means projects light in the vicinity of one supporting portion of the inner peripheral portion of the transparent pipe, and the one supporting portion comprises the transparent pipe of the light projected from the light projecting means. 2. The liquid level detection device according to claim 1, wherein the liquid level detection device is provided between the light projecting means and the light receiving means so as to prevent light reflected on the outer peripheral surface of the light from entering the light receiving means. apparatus.